The present invention relates to matrix printer with transport facilities for a print medium being perforated along longitudinal edges whereby particularly the transport facilities constitute a frame which includes lateral carrier arms being connected in parallel by means of a connection rod as well as a rotatable drive rod; moreover this connection rod and the drive shaft carry parallel slidable and axially symmetrically arranged traction devices.
Transport devices of the type to which the invention pertains and being generally of a nature outlined above are used in matrix printers to advance edge perforated paper sheets or the like which are to be moved in steps or continuously during the matrix print process in which characters are printed on that paper. The print medium may consist of a single sheet or several superimposed paper sheets or webs with inserted carbon layers or the equivalent in order to print multiple copies. Matrix printers are usually equipped with motors, possibly separate motors, for driving the paper transport device, the ink ribbon as well as the print head or a print element carrying shuttle, carriage or the like. Furthermore, the housing or casing of the printer accommodates printed circuit boards carrying electronic control and switching circuits, logic circuits etc. and particularly all relevant electronic components such as diodes, transistors, resistors, capacitors, inductors, integrated circuits etc. These circuit elements together are provided in order to control the print process which includes the formation of characters as well as the control of the various motors or other facilities for controlling paper advance, ink ribbon advance, carriage or shuttle movement and so forth.
It was observed that during operating the electromotors but also the electric and electronic circuits certain structural components of the matrix printers which are not immediately participating in the circuit may receive an electric parasitic charge which interferes with printer operation. Also it has been observed that upon printing by means of needles, styli or the like the engagement with the paper produces such electrostatic charges. The same is true in an augmenting fashion when the paper is frictionally engaged with various parts and guide elements, and this sliding contact clearly contributes to the generation of electrostatic charges. These charges are actually rather elusive and cannot be ascertained definitely and localized during long term printer operation. Therefore there is a danger that electric currents are produced or induced being of a parasitic nature and in an unforeseeable manner penetrate into the electric or electronic circuit elements and interfere with their proper function. It has actually been observed that these currents reach the printer drives and cause its turn-off.